Field of the Invention
The invention relates to a press die and a press machine, particularly, a press die and a press machine for hot press.
Description of the Related Art
For vehicle components, a thinned and high-strength member is used so as to enhance both the safety and economy. For this purpose, so-called hot press is known in which a steel plate heated to high temperature is quenched by cooling the plate with low-temperature press dies. In this method, a steel plate is heated to transformation temperature or higher at which the metal structure of the steel member is transformed into austenite, and the steel plate is formed and rapidly cooled with press dies simultaneously, completing quenching. Conventionally, in order to cool a steel plate rapidly, cooling pipes are provided in press dies. This type of press die is described in Japanese Patent Application Publication No. 2006-326620.
However, only by providing cooling pipes in press dies like in the conventional manner, there occurs a problem in which the press dies are not cooled enough and thus a steel plate is not cooled rapidly enough to obtain a desired strength.